Reveals --ash-enable-fullscreen-app-list flag to chrome://flags.

BUG=434113
R=oshima@chromium.org
TBR=jwd@chromium.org
TEST=manually

Review URL: https://codereview.chromium.org/1146303008

Cr-Commit-Position: refs/heads/master@{#333156}

chrome/app/chromeos_strings.grdp

@@ -1244,6 +1244,12 @@ Press any key to continue exploring.
   <message name="IDS_FLAGS_WAKE_ON_PACKETS_DESCRIPTION" desc="Description for the flag to enable wake on packets.">
     Enables waking the device based on the receipt of some network packets.
   </message>
+  <message name="IDS_FLAGS_FULLSCREEN_APP_LIST_NAME" desc="Description for the flag to enable experimental fullscreen app list.">
+    Enables the fullscreen app-list in touch-view mode.
+  </message>
+  <message name="IDS_FLAGS_FULLSCREEN_APP_LIST_DESCRIPTION" desc="Description for the flag to enable experimental fullscreen app list.">
+    The app-list will appear as fullscreen mode when it's in touch view mode. This flag does nothing outside of the mode.
+  </message>
   <message name="IDS_OFFERS_CONSENT_INFOBAR_LABEL_LEARN_MORE" desc="Text of the Learn More link in the echo dialog.">
     Learn More
   </message>

chrome/browser/about_flags.cc

@@ -1432,6 +1432,13 @@ const Experiment kExperiments[] = {
     kOsCrOS,
     MULTI_VALUE_TYPE(kGestureEditingChoices)
   },
+  {
+    "enable-fullscreen-app-list",
+    IDS_FLAGS_FULLSCREEN_APP_LIST_NAME,
+    IDS_FLAGS_FULLSCREEN_APP_LIST_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(ash::switches::kAshEnableFullscreenAppList)
+  },
 #endif
   {
     "enable-simple-cache-backend",

tools/metrics/histograms/histograms.xml

@@ -58436,6 +58436,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="-610411643" label="enable-printer-app-search"/>
   <int value="-604814313" label="enable-pinch"/>
   <int value="-601384286" label="disable-contextual-search"/>
+  <int value="-589096918" label="ash-enable-fullscreen-app-list"/>
   <int value="-579192400" label="disable-input-view"/>
   <int value="-567920515" label="disable-experimental-hotwording"/>
   <int value="-563980787" label="disable-webrtc"/>